A lithium secondary battery has many advantages such as relatively high energy density, high operation voltage, excellent preservation and long life span, and thus the lithium secondary battery is widely used for various portable electronic devices such as personal computers, camcorders, cellular phones, portable CD players, PDA or the like.
Generally, a lithium secondary battery includes a cylindrical or rectangular case and an electrode assembly accommodated in the case together with an electrolyte. Here, the electrode assembly is prepared by stacking a positive electrode, a separator and a negative electrode and generally has a jelly-roll wound structure or a stacked structure.
Also, recently, a cable-type secondary battery which may be freely modified and thus applicable to various fields has been proposed. The cable-type secondary battery is an elongated battery having a great length in comparison to its diameter and includes a hollow anode layer, a separator surrounding the anode layer, and a cathode layer surrounding the separator.
Korean unexamined patent publication No. 2013-0040160 discloses a technique related to the cable-type secondary battery.
Korean unexamined patent publication No. 2013-0040160 discloses a cable-type secondary battery, which is elongated in a length direction with a horizontal section of a predetermined shape and includes a lithium ion supplying core containing an electrolyte, an inner electrode formed to surround an outer surface of the lithium ion supplying core and having a spiral electrode prepared by spirally twisting two wire-type current collectors having an inner electrode active material coated thereon, a separator layer formed to surround an outer surface of the inner electrode to prevent a short circuit of the electrode, and an outer electrode formed to surround an outer surface of the separator layer and having an outer electrode active material and an outer current collector.
However, the cable-type secondary battery may not be easily mass-produced since there is no technique for automatically assembling the inner electrode, the separator and the outer electrode, and there is needed a countermeasure against this.